Moisture control apparatuses for tobacco material are disclosed in for example Japanese Translation of PCT International Application No. 2001-514023 and International Publication No. WO 01/60186 A1. These well-known moisture control apparatuses are both provided with a rotating cylinder, and tobacco material fed into the rotating cylinder is transferred in the rotating cylinder while being stirred. In this transferring process, water is sprayed toward the tobacco material, thereby controlling the moisture content of the tobacco material.
With such moisture control of tobacco material, however, water cannot be evenly sprinkled on the surface of the tobacco material. Thus, variation tends to generate in the percentage of water content of the tobacco material. The variation in the percentage of water content (uneven moisture control) causes the fracture of the tobacco material when the tobacco material is stirred in the transferring process. This produces fine fragments of the material, which are unsuitable as filling materials for cigarettes, and increases material loss.
Furthermore, the uneven moisture control not only deteriorates the original aroma of tobacco material but also has a damaging effect on the subsequent flavoring process.
Unexamined Japanese Patent Publication No. 6-209751 discloses a moisture control method and an apparatus therefor in which tobacco material is brought into contact with moist air in the process of transferring the tobacco material on a mesh belt. According to such a moisture control method, the tobacco material is not stirred, preventing the fracture thereof. The moist air mentioned in the above publication, however, has the relative humidity close to equilibrium with respect to the moisture content of the tobacco material, so that it takes considerable time to carry out the even moisture control of the tobacco material. Consequently, the invention disclosed in the publication is not suitable for the moisture treatment of a large quantity of tobacco material.